I recommend a mutt myself, since they're generally much healthier than purebreds...very rarely do mutts get breed-related diseases.
Keep away from the Cavalier King Charles Spaniels...they're cute, and pretty bright, but about half of them suffer from serious heart problems.
If you have a LOT of time to spend with this dog (and I mean a LOT), you might consider an Australian Shepherd or Border Collie, as they make pretty good pets. They're both incredibly intelligent dogs, though, and that's where the time commitment comes in. You're going to have to spend a lot of time with either of those two dogs doing really interesting stuff, and some outdoorsy stuff as well. With those dogs, you can teach them pretty complex tasks, and it's a good idea to do just that, because otherwise they'll get bored. If you plan on taking the dog into the woods, you might consider the Aussie Shepherd. You might want to give his or her fur a bit of a trim first, though.
If this is your first dog, keep away from labradors - they're puppies until they're five. And while it's cute, they'll destroy everything you own, because they're so excitable. They make good hunting dogs, though, since they're retrievers.
Cockers are nice, but they have a tendency to piddle on the floor, as well as a high propensity for ear infections and a resultant ossification of the ear canal, which will make them deaf if untreated.
Shih Tzus are also pretty bright lap dogs, and they don't shed much, but their hair requires a lot of work. As they age, they'll have some joint problems, and arthritis is not uncommon. Really sweet, though - when my grandmother's shih tzu died, she was devastated.
Pugs are energetic, so they'll do that heavy snotty breathing thing when they're excited. If you can deal with that, they're wonderfully sweet dogs, pretty smart for something with a brain the size of a coffee bean, and a lot of fun. And shorthaired.
Good luck.